how to draw a square template

 T=100;
f=zeros(128,128);
f(32:96,32:96)=255;
[g1, t1]=edge(f, 'sobel', 'vertical');
imshow(g1);
t1

t1 =

   31.9372

>> sigma=1;
f=zeros(128,128);
f(32:96,32:96)=255;
[g3, t3]=edge(f, 'canny', [0.04 0.10], sigma);
figure,imshow(g3);
t3

t3 =

    0.0400    0.1000